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1.
Thauera selenatis grows anaerobically with selenate, nitrate or nitrite as the terminal electron acceptor; use of selenite as an electron acceptor does not support growth. When grown with selenate, the product was selenite; very little of the selenite was further reduced to elemental selenium. When grown in the presence of both selenate and nitrate both electron acceptors were reduced concomitantly; selenite formed during selenate respiration was further reduced to elemental selenium. Mutants lacking the periplasmic nitrite reductase activity were unable to reduce either nitrite or selenite. Mutants possessing higher activity of nitrite reductase than the wild-type, reduced nitrite and selenite more rapidly than the wild-type. Apparently, the nitrite reductase (or a component of the nitrite respiratory system) is involved in catalyzing the reduction of selenite to elemental selenium while also reducing nitrite. While periplasmic cytochrome C
551 may be a component of the nitrite respiratory system, the level of this cytochrome was essentially the same in mutant and wild-type cells grown under two different growth conditions (i.e. with either selenate or selenate plus nitrate as the terminal electron acceptors). The ability of certain other denitrifying and nitrate respiring bacteria to reduce selenite will also be described. 相似文献
2.
Francisco A. Tomei Dr. Larry L. Barton Cheryl L. Lemanski Thomas G. Zocco Nancy H. Fink Laurel O. Sillerud 《Journal of industrial microbiology & biotechnology》1995,14(3-4):329-336
Summary
Desulfovibrio desulfuricans (DSM 1924) can be adapted to grow in the presence of 10 mM selenate or 0.1 mM selenite. This growth occurred in media containing formate as the electron donor and either fumarate or sulfate as the electron acceptor. As determined by electron microscopy with energy-dispersive X-ray analysis, selenate and selenite were reduced to elemental selenium which accumulated inside the cells. Selenium granules resulting from selenite metabolism were cytoplasmic while granules of selenium resulting from selenate reduction appeared to be in the periplasmic region. The accumulation of red elemental selenium in the media following stationary phase resulted from cell lysis with the liberation of selenium granules. Growth did not occur with either selenate or selenite as the electron acceptor and13C nuclear magnetic resonance indicated that neither selenium oxyanion interfered with fumarate respiration. At 1 M selenate and 100 M selenite, reduction byD. desulfuricans was 95% and 97%, respectively. The high level of total selenate and selenite reduced indicated the suitability ofD. desulfuricans for selenium detoxification. 相似文献
3.
Juan J. Ríos Begoña Blasco Luís M. Cervilla María M. Rubio-Wilhelmi Juan M. Ruiz Luis Romero 《Plant Growth Regulation》2008,56(1):43-51
Selenium (Se) is considered an essential trace element for animals because of its nutritional and clinical value, including
its special relevance in cancer prevention, and thus Se is at present used in biofortification programmes. However, possible
effects of Se application on S metabolism and plant growth are still not clear. Thus, we analysed the effect that Se application
in two different forms (selenate versus selenite) exerts on the S metabolism in lettuce plants grown for 66 days. Our results
indicate that the application of selenite as opposed to selenate does not affect the foliar concentration of S. With respect
to different enzymes in charge of sulphate (SO42−) assimilation, the ATP-sulphurylase activity varies only with the application of different rates of selenate, while the activity
of O-acetylserine(thiol)lyase (OAS-TL) and serine-acetyltransferase (SAT) increase in activity mainly when selenite is applied.
Finally, the concentration of cysteine (Cys) and total thiols (SH-total), fundamentally in the selenate treatments, increased
with shoot biomass. In conclusion, this study confirms that the form and application rate of Se affects S assimilation, selenate
being the more suitable form to improve effectiveness of the biofortification programme with this trace element. 相似文献
4.
Selenium accumulation in lettuce germplasm 总被引:1,自引:0,他引:1
Selenium (Se) is an essential micronutrient for animals and humans. Increasing Se content in food crops offers an effective
approach to reduce the widespread selenium deficiency problem in many parts of the world. In this study, we evaluated 30 diverse
accessions of lettuce (Lactuca sativa L.) for their capacity to accumulate Se and their responses to different forms of Se in terms of plant growth, nutritional
characteristics, and gene expression. Lettuce accessions responded differently to selenate and selenite treatment, and selenate
is superior to selenite in inducing total Se accumulation. At least over twofold change in total Se levels between cultivars
with high and low Se content was found. Synergistic relationship between Se and sulfur accumulation was observed in nearly
all accessions at the selenate dosage applied. The change in shoot biomass varied between lettuce accessions and the forms
of Se used. The growth-stimulated effect by selenate and the growth-inhibited effect by selenite were found to be correlated
with the alteration of antioxidant enzyme activities. The different ability of lettuce accessions to accumulate Se following
selenate treatment appeared to be associated with an altered expression of genes involved in Se/S uptake and assimilation.
Our results provide important information for the effects of different forms of Se on plant growth and metabolism. They will
also be of help in selecting and developing better cultivars for Se biofortification in lettuce. 相似文献
5.
Abstract Sulphate incorporation into glycopeptides appears to be a key event in the development of a number of organisms. An inhibitor of sulphation, sodium selenate, has been used in this study to examine the possibility that sulphation has a comparable role in the development of Dictyostelium discoideum . At concentrations of 0.1 mM and 1.0 mM, exogenously supplied selenate reversibly arrested the growth of bacterially grown amoebae of D. discoideum . In contrast, the effect of selenate on development was minimal. In the presence of 1.0 mM selenate, aggregation and tip formation were delayed 2–3 h and aggregates were slightly smaller; exogenous 0.1 mM selenate had no visible effect on development. However, the possibility that starved amoebae are impermeable to selenate was not excluded. The vegetative growth and development of an axenic strain in the presence of selenate closely resembled that of the bacterially grown strain. Since an inhibitory effect of 1.0 mM selenate on [35 S]sulphate incorporation into acetone precipitable protein was also demonstrated, these results suggest that sulphation is necessary for the growth of D. discoideum . 相似文献
6.
Concanavalin A (ConA) is a tetrameric lectin which is synthesized in the developing cotyledons of jack bean (Canavalia ensiformis L.) as a glycosylated precursor, pro-concanavalin A (pro-ConA). The processing of pro-ConA involves the excision of a small glycopeptide from the center of the pro-ConA molecule, and the ligation of the two polypeptides. In this paper, we show that pro-ConA is associated with the endoplasmic reticulum/Golgi fraction of the cells, and that the processing of pro-ConA occurs in the protein bodies. Processing is a complex process and different intermediate-sized polypeptides appear at different times during cotyledon development. The ConA-related polypeptides which accumulate during seed development may be the products of alternate processing events or breakdown products of ConA, rather than precursors of ConA. When glycosylation is prevented by tunicamycin, there is very little transport of pro-ConA out of the endoplasmic reticulum/Golgi system to the protein bodies; the unglycosylated pro-ConA which is transported is slowly processed. Tunicamycin does not prevent the transport of canavalin (a protein which is not glycosylated) or the transport and processing of the small amounts of glycosylated pro-ConA synthesized in the presence of the drug. This is, to our knowledge, the first demonstration that the transport of a glycoprotein in plant cells is dependent on the presence of the glycan.Abbreviations ConA
concanavalin A
- ER
endoplasmic reticulum
- GlcN
glucosamine
- Mr
relative molecular mass
- SDS-PAGE
sodium dodecyl sulfate-polyacrylamide gel electrophoresis
supported by a grant from NATO 相似文献
7.
The biological reduction of selenium oxyanions is capable of reducing both selenate and selenite to insoluble elemental selenium. In this process, however, bacteria inevitably require expensive chemicals such as yeast extract in almost all cases. Therefore, the reduction of selenium oxyanions with inexpensive alcohol would be more practical. A Pseudomonas sp. strain 4C‐C isolated from a sludge in a wastewater treatment facility was able to reduce selenate to selenite using ethanol as an electron donor for its anaerobic respiration, but could not reduce selenite to elemental selenium. Paracoccus denitrificans JCM‐6892, on the other hand, was observed to be able to reduce selenite to elemental selenium in the presence of ethanol, but not selenate to selenite. Therefore, a mixture containing a suspension of Pseudomonas sp. strain 4C‐C and P. denitrificans JCM‐6892 cells allowed selenate to be reduced to insoluble elemental selenium via selenite in the presence of ethanol and was also capable of reducing nitrate to nitrogen gas. Aiming at simplicity of the recovery process of insoluble elemental selenium, a polymeric gel immobilized mixture of the two bacterial strains was examined using ethanol as an electron donor. The immobilized mixture could therefore reduce not only selenate to elemental selenium, but also nitrate to nitrogen gas in a single step. The gel that immobilized the microbial mixture changed its color during the process to bright red and no red elemental selenium was left in the wastewater. This indicates that the reduced elemental selenium was completely absorbed in the gel. This simple bacterial combination would therefore be effective in the presence of ethanol to reduce selenium oxyanions in various wastewaters containing selenium and the other oxyanions. 相似文献
8.
The antimutagenic effect of selenium as sodium selenite, sodium selenate, selenium dioxide, and seleno-methionine was studied
in the AmesSalmonella/microsome mutagenicity test using 7,12-dimethylbenz(a)anthracene (DMBA) and some of its metabolites. Selenium (20 ppm) as
sodium selenite reduced the number of histidine revertants on plates containing up to 100 μg DMBA/plate. Increasing concentrations
of selenium as sodium selenite, sodium selenate, and selenium dioxide up to 40 ppm Se progressively decreased the number of
revertants caused by 50 μg DMBA. DMBA and its metabolites 7-hydroxymethyl-12-methylbenz(a)anthracene, 12-hydroxymethyl-7-methylbenz(a)anthracene,
and 3-hydroxy-7,12-dimethylbenz(a)anthracene were mutagenic forSalmonella typhimurium TA100 in the presence of an S-9 mixture. Selenium supplementation as Na2SeO3 reduced the number of revertants induced by these metabolites to background levels. The antimutagenic effect of inorganic
selenium compounds cannot be explained by toxicity of selenium as determined by viability tests withSalmonella typhimurium TA100. Selenium supplementation in all forms examined, except sodium selenate, decreased the rate of spontaneous reversion.
Selenium as sodium selenate was slightly mutagenic at concentrations of 4 ppm or less. Higher concentration of Na2SeO4 inhibited the mutagenicity of DMBA. The present studies support the anticarcinogenic potential of selenium and indicate that
form and concentration are important factors in this trace element's efficacy. 相似文献
9.
A protein that binds Concanavalin A (Con A) was detected on Western blots of Spiroplasma citri proteins. Its apparent molecular weight was 84000. It was localized in the plasma membrane. Affinity chromatography on Con A-agarose was used to isolate this protein. The glycosylation inhibitor, tunicamycin, inhibits S. citri growth and seems to block the glycosylation of the Con A-binding protein. 相似文献
10.
Uptake of 35S-labelled sulfate was studied with two sulfate-reducing bacteria, the freshwater species Desulfobulbus propionicus and the marine species Desulfococcus multivorans. Both bacteria were able to highly accumulate micromolar additions (2.5 M) of sulfate, if the reduction of sulfate to H2S was prevented by low temperature (0° C) or oxygen. Sulfate accumulation was highest (accumulation factors 103 to 104) after growth under sulfate-limiting conditions, while cells grown with excess sulfate revealed accumulation factors below 300. With increasing sulfate concentrations added (up to 25 mM), the accumulation factors decreased down to 1.4. Sulfate accumulation in both strains was sensitive to carbonyl cyanide m-chlorophenylhydrazone (CCCP) and thiocyanate, but not directly correlated to the ATP content of the cells. Pasteurized cells did not accumulate sulfate. Sulfate transport was reversible. Accumulated 35S-labelled sulfate was quickly released after addition of non-labelled sulfate or structural sulfate analogues (thiosulfate, selenate, chromate, less effect by molybdate, tungstate, sulfite, selenite). In D. propionicus, sulfate accumulation was independent of the presence or absence of Na+, K+, Li+, Mg2+, Cl- and Br-. Sulfate accumulation was reversibly enhanced at pH 5 and diminished at pH 9. In the marine bacterium D. multivorans, sulfate accumulation depended on the presence of Na+ ions. Na+ could partially be replaced by Li+. Sulfate accumulation in D. multivorans was sensitive to the Na+/H+ antiporter monensin and the Na+/H+ antiport inhibitor amiloride. It is concluded that in D. propionicus sulfate is accumulated electrogenically in symport with at least three protons, whereas for D. multivorans electrogenic symport with sodium ions is proposed. In both species, more than one sulfate transport system must be present. High affinity transport systems appear to be derepressed under sulfate limitation only. The high affinity transport system must be regulated to avoid energy-spoiling accumulation at high sulfate concentrations.Abbreviations CCCP
carbonyl cyanide m-chlorophenylhydrazone
- DCCD
dicyclohexylcarbodiimide 相似文献
11.
Hanna ES Roque-Barreira MC Mendes GM Soares SG Brocchi M 《Protein expression and purification》2008,59(2):197-202
Dps, found in many eubacterial and archaebacterial species, appears to protect cells from oxidative stress and/or nutrient-limited environment. Dps has been shown to accumulate during the stationary phase, to bind to DNA non-specifically, and to form a crystalline structure that compacts and protects the chromosome. Our previous results have indicated that Dps is glycosylated at least for a certain period of the bacterial cell physiology and this glycosylation is thought to be orchestrated by some factors not yet understood, explaining our difficulties in standardizing the Dps purification process. In the present work, the open reading frame of the dps gene, together with all the upstream regulatory elements, were cloned into a PCR cloning vector. As a result, the expression of dps was also controlled by the plasmid system introduced in the bacterial cell. The gene was then over-expressed regardless of the growth phase of the culture and a glycosylated fraction was purified to homogeneity by lectin-immobilized chromatography assay. Unlike the high level expression of Dps in Salmonella cells, less than 1% of the recombinant protein was purified by affinity chromatography using jacalin column. Sequencing and mass spectrometry data confirmed the identity of the dps gene and the protein, respectively. In spite of the low level of purification of the jacalin-binding Dps, this work shall aid further investigations into the mechanism of Dps glycosylation. 相似文献
12.
The trehalase I of Dictyostelium discoideum exhibits characteristics of a typical lysosomal enzyme. The enzyme is glycosylated and carries a number of negatively charged components which cause it to be a very acidic protein. Strain M31, bears a recessive mutation mod A which alters the post-translational modification of several lysosomal enzymes including trehalase. A direct consequence of this mutation is a reduction of the negatively charged components on lysosomal enzymes. This reduction in negativity is observed in the altered chromatographic and electrophoretic behaviour of M31 trehalase.Trehalase I is synthesized during spore germination. Tunicamycin prevents the formation of recoverable trehalase from germinating spores but does not interfere with the germination process. These results indicate that the trehalase I synthesized during spore germination is not required for the successful completion of spore germination. Minor modification in the glycosylation, as seen in strain M31, does not affect the enzymatic activity. However, when glycosylation is greatly reduced by tunicamycin the enzyme is inactive. 相似文献
13.
Kim SY Park JS Chae CS Hyun CG Choi BW Shin J Oh KB 《Applied microbiology and biotechnology》2007,75(5):1119-1126
Indolocarbazole metabolite K-252a is a natural product that was previously reported as a potent protein kinase C inhibitor
with in vitro and in vivo potency. From a biosynthetic viewpoint, this compound possesses structurally interesting features
such as an unusual furanosyl sugar moiety, which are absent in the well-studied staurosporine and rebeccamycin. A cosmid library
from genomic DNA of Nonomuraea longicatena JCM 11136 was constructed and screened for the presence of genes to be involved in the biosynthesis of indolocarbazole K-252a.
Using as a probe an internal fragment of vioB, a Chromobacterium violaceum gene encoding a multifunctional enzyme that catalyzes tryptophan decarboxylation and condensation reaction in violacein biosynthesis,
we isolated a DNA region that directed the biosynthesis of K-252a when introduced into the heterologous expression host Streptomyces albus. Sequence analysis of 45 kb revealed genes for indolocarbazole core formation, glycosylation, and sugar methylation, as well
as a regulatory gene and two resistance/secretion genes. The cloned genes should help to elucidate the molecular basis for
indolocarbazole biosynthesis and generate new indolocarbazole analogues by genetic engineering. 相似文献
14.
The primary sequence of the esterase 6 (EST6) enzyme ofDrosophila melanogaster contains four potential N-linked glycosylation sites, at residues 21, 399, 435, and 485. Here we determine the extent to
which EST6 is glycosylated and how the glycosylation affects the biochemistry and physiology of the enzyme. We have abolished
each of the four potential glycosylation sites by replacing the required Asn residues with Gln byin vitro mutagenesis. Five mutant genes were made, four containing mutations of each site individually and the fifth site containing
all four mutations. Germline transformation was used to introduce the mutant genes into a strain ofD. melanogaster null for EST6. Electrophoretic and Western blot comparisons of the mutant strains and wild-type controls showed that each
of the four potential N-linked glycosylation sites in the wild-type protein is glycosylated. However, the fourth site is not
utilized on all EST6 molecules, resulting in two molecular forms of the enzyme. Digestion with specific endoglycosidases showed
that the glycan attached at the second site is of the high-mannose type, while the other three sites carry more complex oligosaccharides.
The thermostability of the enzyme is not affected by abolition of the first, third, or fourth glycosylation sites but is reduced
by abolition of the second site. Anomalously, abolition of all four sites together does not reduce thermostability. Quantitative
comparisons of EST6 activities showed that abolition of glycosylation does not affect the secretion of the enzyme into the
male sperm ejaculatory duct, its transfer to the female vagina during mating, or its subsequent translocation into her hemolymph.
However, the activity of the mutant enzymes does not persist in the female's hemolymph for as long as wild-type esterase 6.
The latter effect may compromise the role of the transferred enzyme in stimulating egg-laying and delaying receptivity to
remating. 相似文献
15.
蜕皮是许多变态发育昆虫的一种重要生理现象,昆虫通过蜕皮液中的酶对新旧表皮进行分离。已有相关蛋白组学的研究证明,家蚕蜕皮液中具有一种含量丰富的羧肽酶A(Bombyx mori-carboxypeptidase A, Bm-CPA),目前对其作用功能尚不清楚。为了更好地了解Bm-CPA在家蚕蜕皮发育过程的作用,本研究通过生物信息学分析、实时荧光定量PCR、抗体制备、免疫荧光染色和毕赤酵母表达等方法对Bm-CPA进行了研究。结果显示,Bm-CPA具有保守的M14锌羧肽酶结构域和糖基化位点,并且受蜕皮激素(20-hydroxyecdysone, 20E)调控,在眠期和上簇期的表皮中大量表达;免疫荧光染色显示Bm-CPA在眠期的表皮中富集,Bm-CPA抑制剂会导致幼虫因无法蜕皮而死亡;通过毕赤酵母表达系统在体外成功获得大量的重组Bm-CPA蛋白。这些结果为深入了解家蚕蜕皮发育过程提供了一定的参考。 相似文献
16.
Tunicamycin and brefeldin a induce in plant cells a programmed cell death showing apoptotic features
Summary The recent identification ofDAD (defender against apoptotic death) gene in plants suggests that the N-linked glycosylation of proteins could be an important
control point of plant programmed cell death. In this paper we describe the effects of Tunicamycin, an inhibitor of N-linked
protein glycosylation, and Brefeldin A, an inhibitor of protein trafficking from the Golgi apparatus, on sycamore (Acer pseudoplatanus L.) cell cultures. These two chemicals proved able to induce a strong acceleration of the cell death; changes in cell and
nucleus morphology; an increase in DNA fragmentation, detectable by a specific immunological reaction; and the presence of
oligonucleosomal-size fragments (laddering) in DNA gel electrophoresis. Moreover, Brefeldin A, but not Tunicamycin, strongly
stimulated the production of hydrogen peroxide. These results indicate that also in plants chemicals interfering with the
activities of endoplasmic reticulum and of Golgi apparatus strongly induce a form of programmed cell death showing apoptotic
features. 相似文献
17.
When correct folding of protein in the endoplasmic reticulum (ER) is prevented, cells respond to overcome the accumulation of unfolded proteins. This cellular response, which includes the induction of ER chaperones, is called an unfolded protein response (UPR). Although a link between the UPR and apoptosis has been reported in mammalian cells, little is known about this mechanism in plant cells. Asparagine (N)-linked glycosylation of proteins is critical for protein folding in the ER; and tunicamycin, a potent inhibitor of N-linked glycosylation, induces UPR. Growth arrest was observed in cultured tobacco cells treated with tunicamycin. Cell death and induction of Hsr203J, a marker for programmed cell death, were observed in the 24-h period after addition of tunicamycin, following UPR that started within 2 h. These results indicate a strong link between UPR and programmed cell death in plant cells. 相似文献
18.
A thrombin inhibitor was identified for the first time in the gut of the cattle tick Boophilus microplus. Here we present the partial purification and characterization of this new molecule, which was purified from the gut extract
by three chromatographic steps: ion-exchange, gel filtration and affinity chromatography in a thrombin–Sepharose resin. In
SDS-PAGE the inhibitor showed an apparent molecular mass of circa 26 kDa, which is different from the two thrombin inhibitors present in the saliva of this tick. The new inhibitor delays
bovine plasma clotting time and inhibits both thrombin induced fibrinogen clotting and thrombin induced platelet aggregation.
However, it does not interfere with thrombin amidolytic activity upon a small substrate (H-D-Phe-Pip-Arg-para-nitroanilide), which does not require binding to thrombin exosites. Therefore, the inhibitor does not block thrombin active
site, although it must interfere with one of the thrombin exosites. B. microplus gut thrombin inhibitor (BmGTI) is also capable of enhancing activated protein C (APC) activity upon its specific substrate
(H-D-Glu-Pro-Arg-para-nitroanilide), an activity never described before among B. microplus molecules. 相似文献
19.
Libik Marta Miszalski Zbigniew Przywara Leslaw Navazio Lorella Nardi Maria C. Dainese Paola Baldan Barbara Mariani Paola 《Plant Cell, Tissue and Organ Culture》2003,75(2):109-116
We report here the presence of a 58-kDa protein in the cells of Daucus carota L. cultivated in vitro. Two lines of carrot cells are used: wild-type line (wt) and mutant line (ts11). We describe here also presence of this protein in the media of cultured cells. Strong reaction of this intracellular and extracellular protein with an anti-calreticulin antiserum indicates that it is a major high capacity, low affinity Ca2+-binding reticuloplasmin–calreticulin. No differences in biochemical characterization is found between calreticulin purified from the wild-type line and the mutant line. Moreover molecular mass, type of glycosylation and the ability of extracellular protein to bind calcium is found to be indistinguishable from those of the purified intracellular calreticulin. Calreticulin release is attributed to some stress imposed on cultured cells by growth conditions. It is shown that this process can be also induced in CR-non-releasing systems such as carrot somatic embryos by applying a high-cell-density stress. 相似文献
20.
P. Moshitzky I. Miloslavski Z. Aizenshtat S. W. Applebaum 《Insect biochemistry and molecular biology》2003,33(12):1299
The corpus allatum (CA) of adult female Ceratitis capitata produces methyl palmitate (MP) in vitro, in addition to JHB3 and JH III. Biosynthesized MP migrates on TLC and co-elutes from RP-18 HPLC with synthetic MP. Its identity is verified herein by GCMS. MP production is up-regulated twofold by mevastatin, an inhibitor of mevalonic acid-dependent isoprene biosynthesis. Fosmidomycin, an inhibitor of mevalonic acid-independent isoprene synthesis in graminaceous plants, up-regulates MP synthesis by about fourfold. However, it does not depress JHB3 biosynthesis concurrently. This suggests that the initial enzyme(s) in the conversion of 1-deoxy-xylulose 5-phosphate to isoprene is presumably present in C. capitata, but is inhibited by fosmidomycin, and this inhibition diverts precursors to MP synthesis. Phytol, an acyclic diterpene, might be suppressing isoprene biosynthesis by CA, thereby resulting in a fourfold increase in the MP biosynthesis. Linolenic acid is an end-product and its presence in incubation media up-regulates MP biosynthesis by twofold, presumably due to the feedback diversion to biosynthesis of C16:0 and its methyl ester. Biosynthesis of MP is markedly depressed after mating, while otherwise maintained at significantly higher levels in virgin females. MP biosynthesis is significantly reduced in virgin females by direct axonal control but is less consistent after mating. 相似文献